The invention relates to a method for rehydrating a predetermined quantity of food granules with a predetermined quantity of water which is applied to the food granules in a chamber. The invention furthermore relates to a device in accordance with the precharacterizing clause of Patent claim 8 or 13 for performing the method.
A method of the type stated at the outset is employed particularly in vending machines or automatic machines for large kitchens which use water and rehydratable food granules to produce an edible dough which is formed into pieces of edible dough and then fried, boiled, roasted or baked. In this known method employed in automatic machines of this kind, a portion of food granules is fed into a chamber and then rehydrated with a quantity of water corresponding to a predetermined mixing ratio.
Any rehydratable granules which can be converted into an edible dough with water are suitable as food granules. For example, rehydratable potato granules can be used to produce a raw potato dough or a mixture of flour and starch can be used to produce pasta. Herbs and mixtures of herbs can be added to the food granules to suit the personal tastes of the users. To accelerate the mixing of the food granules with water, the water can be heated to a temperature of 80 to 90xc2x0 C.
Thus, U.S. Pat. No. 4,646,627 describes a vending machine for French fried potatoes which produces a potato dough from rehydratable potato granules and water in accordance with the method stated at the outset. The chamber used for rehydration is a cylinder of circular cross section which is open at both ends and the lower end of which serves as an outlet opening that can be closed by a pivotable plate. The cylinder is filled with the entire predetermined quantity of potato granules through its upper open end. A rehydrating unit is then pivoted over the feed opening and deposits the predetermined quantity of water uniformly on the food granules. However, in this arrangement only the upper layers of the food granules are rehydrated, while the lower layers of granules remain unwetted. Uniform rehydration of the food granules with water is therefore not possible.
It is the object of the invention to provide a method for rehydration and a device for performing the method, in which a predetermined quantity of food granules is rehydrated uniformly with a predetermined quantity of water.
In the case of a method of the type stated at the outset, this object is achieved by virtue of the fact that water is first of all spayed onto a portion of the food granules as a fine shower, the said portion forming a first layer of granules in the chamber, and in that food granules are then deposited in layers on the first layer of granules and sprinkled with water in the chamber until the predetermined quantity of food granules and water has been reached.
In the method according to the invention, only a portion of the predetermined quantity of food granules is initially fed into the chamber. The first layer of granules formed in the process is then wetted with water, which is sprayed into the chamber as a fine shower. The fine shower penetrates into the lowermost sublayers of the loosely piled food granules and rehydrates them. With increasing rehydration of the accumulated food granules, the water can no longer reach the lower rehydrated sublayers through the rehydrated upper sublayers, despite its distribution, but collects in the upper sublayers. At this stage of the method, further food granules are deposited in layers on the first layer of granules and sprayed with water. The lower sublayers of the food granules deposited on the first layer of granules, the said lower sublayers adjoining the upper sublayers of the first layer of granules, then absorb the water stored in these upper sublayers. At the same time, the upper sublayers are rehydrated by the additional water sprayed in. Due to the distribution of the water as a fine shower, on the one hand, and the deposition of the food granules in layers, on the other hand, uniform rehydration of the entire predetermined quantity of food granules is in this way achieved.
In the case of food granules which rehydrate relatively quickly, the proposal is to spray each further layer of granules with water after it is deposited. This ensures that the layers of granules are uniformly moistened despite the barrier layers of rehydrated food granules which form and prevent penetration of the water into deeper sublayers.
Food granules which rehydrate relatively slowly can be sprayed with water as they are fed in. For this purpose, water is sprayed onto the food granules falling into the chamber and onto the layer of granules which is forming. This ensures, on the one hand, that the quantity of food granules fed in is uniformly mixed with water and, on the other hand, the rehydration time required for the total predetermined quantity of food granules is shortened since the food granules are rehydrated as they are fed in.
In a preferred development of the method, the water is sprayed in at least partially in a direction normal to the bottom of the chamber on which the food granules can be deposited. This ensures that the entire area of food granules deposited on the bottom of the chamber is wetted with water.
There is furthermore the possibility of spraying in water at least partially along at least one plane tangential to an imaginary cylinder standing in the chamber, in an oblique direction relative to the normal to the bottom of the chamber on which the granules can be deposited. Spraying the water in tangentially produces a circular flow in the chamber which takes the food granules along and not only rehydrates them but also subjects them to a stirring or mixing movement.
At a mean water pressure of 2 to 3 bar, the fine shower should be composed of droplets, the mean volumetric diameter of which is in a range of from 0.5 to 1.5 mm. At a droplet size of this kind, good mixing of the water with the food granules is achieved, on the one hand, especially when food granules and water are fed in simultaneously, since the food granules are sufficiently wetted and, on the other hand, the flight path of the food granules is influenced in a controlled manner by means of the droplet size.
A suitable device for carrying out the method is one in which arranged in the chamber, at a distance from the bottom of the chamber on which the food granules can be deposited, there is at least one nozzle for spraying in the water, which has a cavity that tapers in the direction of flow and the nozzle outlet opening of which, which is connected to the cavity, points in the direction of the bottom of the chamber. The nozzle outlet opening has a separation edge which is acute-angled in cross section and which atomizes the water flowing out.
To spray in the water, use is made, for example, of a single-substance nozzle, arranged in the cavity of which is a swirl insert which has an axial hole and a plurality of radial passages through which the water flows into the cavity in a circular motion. The water flowing in in a circular motion causes a circular flow in the cavity, the axial hole reducing its tangential velocity, with the result that the water is sprayed from the nozzle outlet opening as a fine conical shower. It is additionally possible to control the size of the droplets of the fine shower by regulating the pressure of the water flowing into the single-substance nozzle. If the water pressure is low, a fine shower with comparatively large water droplets is formed. If, on the other hand, the water pressure is high, a fine shower with very small water droplets is formed. This allows the rehydration time to be influenced.
Another proposal is to use a multi-substance nozzle with external mixing which has a second nozzle outlet opening, arranged concentrically to the nozzle outlet opening for the water, for a second medium supplied under pressure. The second medium supplied under pressure atomizes the water flowing out of the first nozzle outlet opening into a fine shower. In this case, the droplet size of the fine shower can be influenced in a controlled manner by increasing or reducing the pressure at which the second medium emerges from the second nozzle outlet opening. For reasons of hygiene, compressed air, steam or a mixture of compressed air and steam which emerges from the second nozzle outlet opening are particularly suitable as the second medium. Also conceivable is the use of a multi-substance nozzle with internal mixing, in which the water and the second medium are combined in the nozzle body, it being possible to influence the quantity of water by regulating the inflowing quantity of the second medium.
In a preferred embodiment, the chamber of the device is designed as a cylinder with a symmetrical, preferably circular, cross-sectional shape, in which the nozzle is arranged concentrically and sprays the water in in the direction of the longitudinal axis of the cylinder. The symmetrical shape of the cylinder leads to uniform distribution of the fine shower which is sprayed in and falls on the layers of granules.
In addition, a piston which can be displaced in the longitudinal direction of the cylinder and on which the nozzle is mounted can be provided in the cylinder. By means of this piston, the food granules rehydrated in the cylinder can be pushed out of the cylinder via a discharge opening and, for example, pushed through a forming device. It is furthermore possible to adjust the distance between the nozzle and the surface of the respective layer of granules fed in since the nozzle is mounted on the displaceable piston, allowing the nozzle to be moved upwards as the level of food granules in the chamber rises and ensuring uniform spraying of the entire surface of the layer of granules at every point in the process.
In a second embodiment of the device for carrying out the method, at least one nozzle is arranged in such a way at a distance from the bottom of the chamber on which the food granules can be deposited that the water is sprayed in along a plane tangential to an imaginary cylinder arranged in the chamber. In this second embodiment, the food granules are not only rehydrated but also taken along by the tangential injection, which produces a circular flow in the mixing chamber, and a stirring or mixing movement is brought about.
To reinforce the circular flow of the food granule/water mixture in the chamber, the water can be sprayed in at a plurality of points in the chamber, either simultaneously or at time intervals. For this purpose, the injection points in the chamber can be arranged in a common radial plane, preferably being distributed uniformly over the cross section of the chamber. Arranging the injection points in this way, especially distributing them uniformly over the cross section of the chamber, sets the food granules uniformly in motion in the chamber at a plurality of points and the formation of accumulations of food granules is avoided.
In another advantageous version of the second embodiment of the invention, the injection points can also be formed one above the other, i.e. in radial planes arranged one above the other, producing circular flows in the various layers of granules, particularly where there are large quantities of granules in the chamber. If the injection points are arranged in this way, the water jets in the various injection planes can also be aligned in opposite directions, thereby producing opposite circular flows in different layers of granules, these opposite flows improving the mixing of the food granules with the water sprayed in.
It is furthermore particularly advantageous if the water is sprayed in obliquely to the longitudinal axis of the chamber. Spraying the water jets in obliquely ensures that the various layers of granules are mixed with one another, in addition to the circular flow already described.
In a development of one of the two devices, a chute which opens into a feed opening formed in the chamber is arranged laterally on the chamber for the purpose of feeding in the food granules. In this case, the chute is preferably arranged at an angle of 10 to 20xc2x0 to the longitudinal axis of the cylinder. A chute of this kind is suitable, in particular, for use with food granules which rehydrate relatively rapidly. By virtue of the steep arrangement of the chute, the food granules can be fed into the chamber at high speed, thereby preventing rehydration of the food granules in the chute.
In another embodiment, a chute which can be pivoted into the chamber and in the outlet opening of which the nozzle is arranged is used to feed in the food granules. This pivotable chute is used, in particular, if the food granules are to be sprayed with water even while they are being fed in.
In a preferred embodiment of one of the two devices, the cylindrical chamber has a circular cross section and the piston has a rotary drive which can rotate the piston about its longitudinal axis. Raised portions, by means of which the food granule/water mixture can be stirred, are formed on the underside of the piston.
The mixing of the food granules with the water sprayed in can furthermore be improved if a heating device is provided on the chamber. By means of the heating device, the chamber is heated to a temperature range of 80 to 90xc2x0 C., with the result that the water sprayed in does not cool down but maintains its temperature of 80 to 85xc2x0 C. and thus penetrates better into the finely porous food granules.
As a closure for the discharge opening of one of the two devices, it is proposed to provide a closing plate which is mounted outside the chamber and can be pivoted in the plane of the plate. The closing plate is moved by means of its own drive, for example a positioning motor. To prevent the closing plate from sagging when the discharge opening is closed and the piston is compacting the edible dough, the closing plate can be supported by rollers in the region of the discharge opening or be held by a locking mechanism. If a heating device is provided on the chamber, as already described above, it is furthermore advantageous if the closing plate is fitted with a heating device which heats the closing plate at least partially in order to prevent condensation of water on the closing plate.
The use of a flap or slide is also possible instead of a pivotable closing plate.
In order to shorten the strips of dough emerging from the forming device to the desired length, it is furthermore proposed to provide a dough cutter on the chamber. Suitable dough cutters are, for example, a wire which can be moved through the area of the discharge opening, transversely to the latter, or a cutter blade which can be moved through the area of the discharge opening. In a preferred embodiment, the dough cutter can be pivoted through the area of the discharge opening together with the closing plate. This makes it possible to use a common drive for the closing plate and the dough cutter. Once the closing plate exposes the discharge opening, the dough cutter is in the stand-by position and cuts the strips of dough as soon as the drive of the closing plate is activated again. Instead of a dough cutter which is pivoted backwards and forwards several times underneath the discharge opening, it is also possible to use a plurality of dough cutters, which then cut the strips of dough in succession.
A wire as a dough cutter can be stretched between a hub of the closing plate, the said hub being arranged on the pivoting axis, and a web projecting radially from the hub. Instead of a wire as a dough cutter, it is also possible to use a cutter blade projecting radially from the hub. In a preferred embodiment, the dough cutter is in the form of a cutter blade on the peripheral edge of the closing plate.